Otherwise, if the sore appears on soft tissues inside the mouth, it may be a canker sore
. Cold sores presents with a small, painful, fluid-filled blisters
on a raised, red, painful area of the skin. Pain or tingling, often precedes the blisters by one to two days. Once you've had an episode of cold sores, the virus lies dormant in the nerve cells in your skin and may emerge again as an active infection at or near the original site.