My eastern garter has developed a throat lump on the under side of its throat. I noticed it the day before yesterday but it seems to have doubled in size, now.

Is this cause for concern? Should I rush to a vet, or wait and see how things develop? He doesn't seem bothered by it at all. He's eating normally and maintaining the same level of alertness / activity as before and it doesn't seem to cause him any pain. I touched it when I first noticed it and it was pretty soft, not hard.

I feed him nightcrawlers (nothing that could have wounded it from inside). Bedding is natural top soil without additives and some gravel to help shedding. I've had this snake for a year and a half and never had this problem before.

I read that it could be a respiratory infection due to too much variation in temperature. I don't believe the temperature drops enough for that to be the cause.

I'll try to take pictures and post them soon, but I wanted to fire off this post as quickly as possible.