Hmm, if I had my dogs (or me!) tested every time they (or I) got a tick, we'd never get out of the vet's office, LOL. Was it a big tick? If so, Lyme disease isn't likely. Deer ticks (the ones that spread Lyme) are itty-bitty, like the size of a pinhead or smaller. There may be other diseases spread by dog ticks, but this depends on your area. I agree that calling your vet to ask which diseases are common in your area would be a good idea.