I have pains in my inner ankle when training for the marathon what shall i do?

Pedorthist: You may wish to check with a podiatrist or a pedorthist to determine if your shoes are providing the correct support for your feet & ankles.

Post tib tendonitis: You probably have posterior tibial tendon tendonitis. Common in long distance runners. It is usually tender along the inner or medial ankle. Behind the malleolus (inner ankle bone) and extends into your arch. It can get worse if you don't treat it. Start with ice block massage, wear a shoe with a good arch from morning til bed, nsaids and toe raise type exercises.

Support & adj. run: This is probably an overuse injury of the tibialis posterior tendon. You need to adjust your training. Cross train with a bike for cardio fitness, and add a good arch support from a sport store. If persists, you may need foot orthotic bracing and time off to rehab. I don't know how much time you have, but his can become an injury that can keep you out of this race. They'll be another.