In reply to sazmaz: I've had this a few times and my girlfriend has had it worse than me. There's a few things you can do to really help it and top of the list is to increase the flexibility in your calves and also the front of your legs. Do this with conventional stretching and with foam rolling/massage/golf ball. 'Smashing' the muscle just to the side of your shin bone with a golf ball or your hands will really hurt, but with time it will get better (ie flexility, blood flow, etc increases) and this will massively reduce the pain when running. The muscle might be so tight that it feels like bone. Secondly, stop running for at least two weeks to let the inflammation go down. Ice the affected area.
If, when you return to running, it's not gone, see a physio. It might cost £100 for a couple of appointments but if you enjoy running then it is money well spent. Also, check your shoes and gait. If you are running 'barefoot-style' then your chance of this sort of injury is almost certainly far greater.