I gave up running largely because of chronic shin splints, though I had a different kind (medial tibial stress syndrome, it's now called). I never really had any issue with the tibialis anterior muscle, though strains of that muscle (and the connecting extensor tendons) are also called "shin splints." If you had a lot more ankle action from the change in your ride conditions, you could easily have overused that muscle. Maybe your form wasn't perfect either. I don't think it's a common cycling injury, but I wouldn't say it's impossible or anything. I think that the ice will help the swelling, but massage may help it heal faster. So, massage until the area is flushed (with some sort of lotion, not just till you rub the skin red), and then follow with ice. Obviously take it easy, but I think you can probably still ride some, just err on the flatter easier side, and don't ride if it is bothering you just sitting around.