OK, thanks for the additional info!
There are a number of things that can cause a lesion like that.
The most common reason for a lesion like that would be an insect sting. This is a little less likely in the winter, but sometimes a spider bite could do this. If this is the case it really should improve over the next few days.
It could be a bruise. If your dog plays with other dogs it is possible that someone nipped her.
It is possible that it is a localized area of skin infection. However, we usually see crusting and flakiness with this.
While ringworm is possible, it is unlikely. Ringworm is a fungal infection and usually causes flakiness and dandruff. It doesn't usually cause a red ring in dogs. Also, it is very uncommon in dogs.
It certainly won't hurt to put some neosporin/polysporin on it a few times per day to see if that will discourage the licking. But, if it hasn't gone away in 3-4 days or if it seems like it is getting worse, then a vet visit is probably a good idea.
I hope this information helps! If you have more questions regarding this problem, just hit reply. If I am online I will respond right away. Otherwise I will respond as soon as I come online again. Or, if my answer is sufficient, then please hit accept. Thanks!
The above is given for information only. Although I am a licensed veterinarian, I cannot legally prescribe medicines or diagnose your pet's condition without performing a physical exam. If you have concerns about your pet I would highly advise contacting your regular veterinarian.