Act causing slight harm is defined under section 95 of ipc. Provisions under IPC section 95 explained here:
What is Section 95 IPC:
Nothing is an offence by reason that it causes, or that it is intended to cause, or that it is known to be likely to cause, any harm, if that harm is so slight that no person of ordinary sense and temper would complain of such harm.
Section 95 IPC Explanation:
This section means any act which is even intended or unintended to cause slight harm which a person of normal state of mind would not complain about will not be constituted as an offence. For eg A slight pat on ur friend’s back might cause a slight harm for a second or two but no ordinary person will complain about it.