Suggest Remedy For Ring Shaped Bruise On Left Underarm

I have what appears to be a ring shaped bruise on my left underarm. It's perfectly circular with a clear spot in the middle and probably a little less than an inch in diameter. I was recently at a friends house (two weeks ago and this past weekend, Vienna OH) and ticks like to frequent the areas surrounding their house. I did check myself for ticks, I found a big dog tick but it didn't appear to have been embedded anywhere in the skin. I didn't see any deer ticks. The bruise doesn't look red and rashy or like a bulls-eye, but the shape of it is still a little unnerving considering I've been in a tick infested area. Could it be that it's still a strange variation of the bulls-eye rash associated with lyme disease? If it is lyme disease is it something I should take care of immediately? or can I wait till the morning to see a doctor?