Is my baby ready to sit up?

So lately my baby boy is ready to sit up, 3 months, he gets mad if you let him lay on his pillow unless you sit him upright but his head still bobs a bit. I don't know if his actually ready but he thinks he is and bouncing by his legs and trying to sit and just get mad if told other ways.

Should I just let him be and help him or should I not? This is my first I read I could end up hurting him if you rush certain milestones which I don't wanna do but I don't want to stop him if he thinks he's ready.

EDIT: Thank you guys for the advice and reassurance!