If it isn't eating anything, just remove it/kill it and don't think twice about it.
If it's a real pest relative to marijuana, you'll know soon. So, if you can identify it through google images or another person here, you can be more proactive.
pesticides, traps, etc.. the typical options. I'd just start over if it is a real problem, since it's so early. Thoroughly clean area... outdoor? may be impossible to avoid?
I don't spray any pesticides or chemicals on things i will later smoke, lol. Start over, if it's a real pest, or if you think it's inevitable problem given grow area, find a way to combat it without poisoning yourself in the end.