You've received GREAT advice above.
I just want to emphasize two points:
1.
You describe the same behavior at home, where presumably you can tune his level of challenge, which suggests that the behavior is not principally originating from lack of challenge...
2.
The thing is, if someone doesn't like how you are touching them, you have to stop. It doesn't matter if you're bored, if you're having a hard day, or if you've always tested rules. The other kids have a right to feel safe in their classroom.
Are you working with him at home to reinforce that it does NOT matter whether he "feels like" touching someone or "wants to" poke someone... he must repeat to himself the rules about not violating personal boundaries and he must make his hands (and feet and other body parts) to obey those rules.
Having clear consequences which are known proactively and which have consistent enforcement and follow-through often help.
Unwanted bodily contact can quickly be interpreted as assault, sexual assault, or as carrying perceived overtones of racial/ethnic/cultural inequality.
