It could be strep, it could also be an infection in your throat from your sinuses. I get it all the time. You should get it checked out, and try drinking ice cold drinks if it hurts.
Strep usually looks red with white pus lying on the tonsils or pharynx. Ulcers can be from viruses, we call them aphthous ulcers. If it worsens or persists have a doc check it out.