Need to evaluate when you get there. Take a look at the other signs as well: crest, orbital fat. They can blow up very quickly after a long feast on grass. If he is obviously in trouble, then cold soak may or may not help. You'll know if it's helping fairly quickly.
Depending on the decision or results of above, if he were here, I may or may not boot/sock him. Can you check him later in the evening?
Unless he's in such pain that he's not eating and drinking, skip the bute so you can better evaluate again tomorrow.
Nancy C in NH
ECIR Moderator 2003