Talk to Pediatrician on Irritation, Not Sleeping, Cries All The Time

My nephew is of 8 months and he started walking (not ny his own yet) and teeth b nklna start hgae hn, 2 are already grown. Problem is that he cries all the time, never fall asleep and is not taking his diet properly due to which his health is disturbing too. Kindly recommend any medicine or something which have no side effects but give him realef from the pain. We are currently giving him Bio21 for teething and some times penadol syrup when his body heats up.