Is it normal i feel bad about this?

I can totally understand that, like you want to keep innocent childhood-type things separate from the more adult stuff, and you feel like you've spoiled its innocence and purity now that you've mixed the two. It was probably exactly the reason that you wanted to maintain its purity that caused the temptation to masturbate with it, because it became a forbidden taboo. You should try to realise though that there's nothing wrong with sex or masturbation, it's not dirty or sinful, it can be a healthy, beautiful and loving thing. It's all how you view it yourself, the same with this situation with your plushie. Like you said, you can't notice anything different with your plushie, so the only thing that's different is how you view it now in your head. You can view it as tainted, or you can view it as just as pure and innocent as it was before, which you really should.

its an inanimate object and dont matter really

but maybe you can learn a lesson from it and think twice about doin questionable shit with the sentient in the future

I did the same thing to a plushie. Made a hole in it and latex inside.

It's perfectly normal and it's fine, but if you get even more conscious you'll find you're sad because it has meaning, if you remove the meaning there's the retraction of getting back to the feeling and feeling bad, so yes the evil is there.

There's really no point in ruining things you made yourself. Ruining it is the equivalent to wasting time and effort that could be used elsewhere. Though there's no need to panic over it. He'll be fine. All you gotta do is clean him, buy a sex toy, and use the sex toy instead.

You molested him

It's sort of a sense of regret, like as if I did something terrible to him..