In my uneducated opinion (lol), I would say that yes it could very well be an allergy. Some allergy cause you sinuses to drain into your throat causing sore throats. Alot of these times, these sore throats only bother me at night and lessen during the day. If you feel that you are going to be bothered by it, take an antihistamine an hour or two before you go to bed. This will dry you up long enough to sleep and not awaken with a sore throat. Antihistamines usually cause you to become sleepy and you could awaken groggy the next morning. Untill you know how a certain brand will affect you, take it early enough to be able to sleep it off. Of course with any drug,read the fine print on the box. If you get to the point where your throat feels tight and you are having problems breathing, you need to get to a Dr. THEN...
I know this was more than you asked for, but I got on a roll. Hope you are better today!!! Of course, if it lasts and your throat looks funny, see a Dr. anyway.
God Bless you!