My implant screw was wobbly for few days now has fallen out. It is a back molar. Can I just have it screwed back in?

It sounds like the healing abutment used to keep the gums out of the implant has loosened up and come out.  This is an easy problem to resolve your dentist will need to screw it back in and maybe trim some overgrown gum.

yes, its a very simple proceedure, and they can come out, because they are not set with a torchimeter,  until you receive the final crown, the healing cap, can fall down, but put it in, as soon as posible, unfortunately you cant do it. because has a place for a screwdriver.