Too soon for growing pains??

My son just now started walking, which is fine. But its like he discovered it all in one day. He went from standing to taking steps and did it over and over.

Tonight he keeps waking up crying like hes in pain. I know its pain because of his cry and the fact that breast feeding doesnt stop the crys.

He will stop for a few minutes then cry a few. Its off and on.

Im pretty sure its not teething.

Could it be growing pains or pains from "working out" his leg muscles a lot today?