No, I highly doubt this is "teaching him aggression", as that's how birds play with toys. He is most-likely acting the way he is with that specific toy because it has a bell on it and it makes noise, which really gets him all riled-up (in a good way, lol)...I've always noticed that any and all of my parrots, from my very first Budgie when I was 6 to my current birds now, get much more "crazy" over toys that make noise, specifically the ones with bells on them...I grew-up in a house that bred both English and American Budgies and also had them as pet birds, and I currently have 8 of them that I bred and hand-raised myself...And with Budgies I've always found that they are happy as can be with the really cheap, plastic bird toys and actually prefer them to the much more expensive toys...And most of the cheap, plastic bird-toys have bells on them, and they always go insane while playing with them...
All of my birds do the same thing that you're describing with the toys that have bells on them, such as the plastic balls strung together with a bell on the end, plastic rings strung together with a bell on the end, etc. They "beak" them very hard and very fast, causing the bells to make noise, and they keep doing it over and over again. And it does look like they are getting kind of "aggressive" with them, but that's not what they are thinking, they're just playing...Oddly my Senegal Parrot plays with his toys in a way that is closest to the way the Budgies play with their toys, he'll start "beaking", or quickly poking/striking the toy with his beak, and he does this over and over again, and then he gets what I like to call "Crazy-Eyes", lol. I've always called it that since I was a little kid with my first Budgie, Keety. They start playing with a toy and they get really excited, and they start doing what you're describing your IRN doing, they start quickly striking the toy over and over again with their beak, and then the feathers on the top of their head stand straight-up, and then their pupils constrict and they have "Crazy-Eyes!" I love watching the Budgies play like that, and both the Budgies and my Senegal get "Crazy Eyes" when I start playing with them too...They start "beaking" my finger and then I "beak" them back, etc. It does look a bit aggressive, but it's not a "bad" thing...
I think your IRN is just really enjoying that particular toy, and that's a good thing. A lot of birds don't really ever find a toy that they get excited about, or play much at all in-general, while some parrots don't even know how to play with toys or what toys are because they weren't given toys in their weaning-cage by their breeders. So this is a good thing that your IRN plays with some excitement and vigor...
Just make sure that you always have a back-up string of plastic balls with bells, lol, in case he breaks the one in his cage...You made your own, that's cool, but as a quick back-up they only cost $2 at Petco...And you actually might try buying a few more of the cheap, plastic bird-toys they sell at Petco. There are tons and tons of different types of the plastic bird-toys (I believe they are made by Pen-Plax and JW), it's funny but they do often prefer these to the expensive bird toys...Try a few different of the plastic bird toys, one that spins around, one with a mirror, etc. They actually have a couple of these cheap, plastic bird-toys that make the bird do foraging-activities or learn to do a certain task, and this can keep them busy for hours! I have a bunch of these for my Budgies, but my Senegal, Quaker, and Green Cheek all love to play with them too, so I bought a ton of them for them to try...One is a Ferris-Wheel that goes around and each "seat" is a little dish that you put a treat in and then have to learn to spin the Ferris-Wheel around in order to get to the treats; one is a weight-lifting toy that attaches to the cage-bars and where they have to pick-up barbells and put them in the slots on a rack; one is a basketball hoop/backboard with a ball that they have to put through the hoop; there's a bunch of them. And they'll sit and work on them for hours once they figure out what they are supposed to do; that Ferris-Wheel with the seed-cups as the seats is genius, lol...And the best part is that most of them cost between $2-$5! (There is also a Mirror-Ball (Disco Ball) that is reflective and that they absolutely love to beak the hell out of!)