Is it all your thighs, hamstrings and quads. If all then probably just a nice case of overuse, too much too soon, I have found taking whey protein liquidised with a banana and skimmed milk good for recovery. If the soreness is predominantly in the front then there may be a bit of imbalance with your thighs sharing the load and your saddle may be a touch too high making the quads do more work than the hamstrings and glutes.