my shih tzu dog

Question
As I brushed my dogs hair on the top of her head I noticed what appeared to look like a scab on the comb.  I then looked through her hair and on the top of her head I noticed a big sore.  Nothing has happened as far as an accident, I am just unsure of what this could be.

Answer
It could be a self-inflicted wound that you found or a scrape from her running into something in the yard or house.
Unless it spreads, just watch it and see if it heals on its own.
If it isn't gone in about a week and a half I would have it looked at.