Blood Blister on Dogs lower lip!!

Hello everyone, Today we came home from the park and when I looked at Sadie's lower lip she has what looks like a blood blister I have no idea where she got this from. It is not a tick that's the first thing I thought, it's pretty large so I put neosporin on it for now anyone know what this could possibly be? I will be keeping a very close on on it to see if it gets larger then of course vet time. I am hoping this is some sort of insect bite. Any advice is appreciated.
Thank You

She probably just pinched her lip against a stick or something. I would just keep an eye on it and if it seems to not go away, or looks like it opened up, bring Sadie to the vet.