Swollen felock

[catherine22]

The end of last week the outside of my horses offside foreleg has swollen up at the fetlock, it is only on the outside nothing around the tendons or around the front and nothing coming up from his pastern or down from his cannon bone. Farrier has been out to check shoe which is fine, he's not lame but i have had him on bute since monday with no difference in the swelling, doesn't change with work or day off. He doesn't have a temperature, am thinking now is the time to call the vet unless anyone has any other ideas what it could be? He lives out
Thanks

 

[HandTS]

Autum flush in grass may have caused this, my horse came in on Sunday with one swollen fetlock both by Monday, Tuesday put her on old field not as much grass, both are back to normal last night, could be the same.