Mouth ulcer in 5mo EBF

[KikiShack]

Is this normal or is it caused by something? DD has what looks like a mouth ulcer, it's white and as big as a small pea but flat, just inside her top lip to one side.
I can't tell if it's causing her pain or not, she doesn't like me rooting around her mouth at the best of times!
Is it an ulcer? Good old google said it might be thrush, but it is very localised and my breasts don't seem to hurt. Google also suggested herpes! DD does have a gooey eye, but it's not red and she's always had it, so I'm not to bothered about it being herpes.
Any advice very welcome.

Maybe the start of hand foot and mouth? They can get a very mild version of this, and so might not have many of the blisters.

I've checked her mouth this morning and she has her first tooth!! On the bottom, right opposite where the ulcer is on the top, so maybe it's where the spiky tooth rubbed against the inner mouth before I noticed the tooth. Does this sound at all sensible? I'm really hoping it isn't HFM, I don't want to catch it!!

I've checked her mouth this morning and she has her first tooth!! On the bottom, right opposite where the ulcer is on the top, so maybe it's where the spiky tooth rubbed against the inner mouth before I noticed the tooth. Does this sound at all sensible? I'm really hoping it isn't HFM, I don't want to catch it!!

I've checked her mouth this morning and she has her first tooth!! On the bottom, right opposite where the ulcer is on the top, so maybe it's where the spiky tooth rubbed against the inner mouth before I noticed the tooth. Does this sound at all sensible? I'm really hoping it isn't HFM, I don't want to catch it!!