I found a tick on my son, has had rash for about 2 weeks, is this a concern?

my 2 year old son , has had several different looking rashes the last couple of weeks, it has been a course of 4 weeks, one weeks it was a rash that looked like scarlet fever, the rash, no other symptoms, just the rash, then this week he had a fe difrant looking patches of skin abut dime size , all over his arms and shoulders, the dog say ( kids get rashes all yr time) no biggie!! well this morning i was fixing his hair and found a tick! on the back of his neck, his hair was covering it, mu dogs don't have ticks, he could have gotten it form the dog park!! so dose the rash have something to do with the tick???