I was lifting a box and pulled out my back with a possible pinch nerve, hurts mainly on the right hand side lower and mid. what do i do?

Take it easy: I would avoid heavy lifting, take some Ibuprofen or naproxen, and use heat or cold on the affected area three times a day for 20inutes. If you get no better see a doctor.

Rest and recuparate: This is more likely a pulled muscle, but could be a pinched nerve. Try heating pads, nsaids and rest to start with. The symptoms should resolve.If they persist consider going to an urgent care center.