Before I get started, I'm likely taking my dog to the vet tomorrow, but in the meantime, I'm hoping to get any info/opinions I can.

A few days ago, on one of my dogs, I found three small isolated bumps. Each feels like a small ball-bearing (smaller than a BB) under her skin. I guess they seem very similar to a very ingrown hair. One behind her ear, one on her shoulder and one on her flank.

I haven't taken any pictures b/c they're very difficult to see through her fur much less get a picture of. There really isn't much to see anyway. They do not appear to be red or irritated. If I squeeze, there is no discharge and very little give. She does not appear to be in any discomfort.

This morning when I checked, the largest (on her shoulder) did have a small blackish center. Scraping it with my finger nail, it came off and appears to be a small scab, whether puss or blood I can't tell. There was a very slight amount of discharge under where the scab was. Once again, she appears to be in no discomfort nor does the area seem sensitive. I treated with a triple anti-biotic.

I just moved to a house in the woods and there are plenty of ticks and spiders around. My thought is insect bites, but I worry b/c there are brown recluse around, although the symptoms don't seem to match what I've read. For what it's worth, both her and her brother are on Nexgard and I've not found a single tick actually having bitten them, although I have found a couple crawling on them after walks.

Any opinions?

I'd not worry about recluse bites, they are surface biters they aren't going to bury themselves into the fur to get to the skin.  Besides if it was a brown recluse the damage would already have been done.

Honestly, if your dog isn't in pain, I'd suggest monitoring it for a few days to see what happens.

Could be tick bites where the tick has backed out (or been scratched off, with the head was left in causing infection).  Or it could be some blocked follicles (doggie zits).  

A vet visit isn't a bad idea - get a Lyme test.  Probably not an emergency though.

Thanks guys, I appreciate the feedback. I try to take good care of my dogs but don't necessarily baby them. I don't have any idea what this which is why I'm a little concerned.

hate to tell you this, but i had a BIG chocolate Lab that started developing those all over,
they started festering after a few weeks; turned out to me mast cell cancer.

I was living in NoCal at the time right next to UC Davis Vet school; my vet knew
everyone over there & he said there was nothing they could do.

Hope it doesn't turn out like that, but love the dag & do the best you can.

I appreciate the well wishes and I'm sorry about your lab.

In this case things seem ok. By the time I got a non-emergency vet visit the bumps had started to significantly reduce so I ended up not taking her in. They're just about gone and no more appeared so I'm going to go with some sort of insect bites. All seems good.

glad to hear that