If it's more than one or two, then it's not likely to be nothing.
Can you have a good look at the base of the wool fibres? On the moorland farm we had problems with keds one year in one batch, and sucking lice another. You have to identify the beastie so you get the treatment right - or you can treat with Crovect if you have it on hand, and if that doesn't clear it up, use Dectomax.
I expect the S word has gone through your mind... fresh skin scrape to the vet (or they may ask you to take it straight to the vet labs) to eliminate that possibility.