First of all, you just ran a marathon...26.2 miles and generally, you will have aches and pains. If you had aches and pains before the marathon, then the marathon will increase those aches and pains.

There are some differences from shin splints and stress fractures and shin splints can turn into stress fractures but the treatment is the same...NSAIDs, ice and rest of the effected part. With shin splits, the pain goes away after running 2-3 miles where stress fractures the pain increases as the running progresses. Also there will be point tenderness at the spot...meaning when you put your finger on it...it will be painful. The pain radiating usually indicates nerve or tendon/ligament.

I had lots of shin problems when I started running longer distances that just kept getting worse and I kept running on it thinking it would eventually go away. I finally just stopped running for 5-6 weeks and just swam, walked, biked and use the elliptical. After about 5 and half weeks, I gradually worked my running back into my training and everything has been fine since then.

Give it a couple of days rest...go ahead and walk, swim...NSAIDs (drugs with aspirin, ibuprofen, naproxen...not Tylenol) and ice will help. If it doesn't seem to improve go see your marathon running doctor for his diagnosis and recomendations.