Front leg problem, need advice!

Hi. Im back to running after 3 month off ( winter time and laziness)... Im not pround of it but IM BACK. I used to run progressively ( starting with 10 min, 10.11.12.13.14.15.16....etc...) until I reach my target time, which is 30 minutes. I experienced a problem when running:

After 10 continuous running minutes, I felt that my muscles in my front leg ( around tibia) when so tense ( or contracted) that I wasnt able to run. I had to stop because It was painful. I know its the muscle because I touched it AND it was hard like a rock because it was anormally contracted. Why this happened? What to do to prevent it? I felt no pain an hour after the run. No injury were felt the day after. But, the same thing happened on my next run. Running on grass helped me a little.

NEED ADVICE!!!

Hi running on grass lol are both of your legs the same size before or after a run? in a relax time or exercices time. are they both hard after 10 minutes? or 11? 12?.... the big Questin is what am wronga witha mi lega. better find out and fix so you can run 10 miles or 11 or 12 miles. :>