am I stating the obvious here or are we already talking about a pretty classic case of shin splints, I know shin splints is an big umbrella term used to describe almost any lower leg/tibia pain so differentiating between tibial periostitis, exertional compartment syndrome, tib post tendinopathy or perhaps some form of neural component is paramount to success in effectively treating this condition. A recent paper i read suggested that soleus was the primary cause of medial tibial stress, and tib. post. secondary, might be something to think about/assess. I guess like the others have said rest is definately on the cards either way, if just walking flares it up then maybe ice it down for a while afterwards and soft tissue massage.
Additional Comment I forgot:
also a friend of mine who does a lot of sprints swears by dry needling, he had them for years on and off, a few treatments with DN and the problem was solved.