I'm sure finding a bump that you don't know the cause of is very scary- I'm sure you don't have HIV, or anything like that. You mentioned ticks- do you mean fleas or has your dog brought in several ticks? Are you worried a tick may have caused the bump?
Bumps sometimes just happen, but it's certainly something you can keep an eye on. If it changes in size or starts to hurt, or itch, don't be afraid to tell your parents and ask them to take you in for a check up.