My 3 month old baby was having teething problem as he used to put his hand on his mouth .. what should I do..?

A. hi ,   teething, exploring, hunger, self soothing , sleep , tiredness are common reasons. babies at this age put everything in mouth. get  a teether of good company, BPA free for baby. also get some plastic toys with smooth edges , check for good quality . also you can give some clean washed ccolorful cloths to baby to play with. they love different textures.