I had accident last year, had fracture in right arm, so got my radial head removed and doc put a nail an wire around, for how long can I keep it inside?

It depends. From your description of your accident and injury, it's sounds like you had a radial head resection and some other forms of internal fixation. Orthopedic plates, screws, rods, wires and pins are commonly used surgically. They can typically be left inside your body without harm, but may require removal if they become noticeable or symptomatic. Presence of metal internally is not a problem.