My pitbull has bumps like mosquito bites after grass. Are they hives?

You may be describing hives. They just look like small patches of fur that stick up a little more than other areas, and the length of pitbull fur makes them very prominent! If you haven't bathed her since rolling in the grass, I would recommend doing that to wash off any allergens that she may have come in contact with. If they don't get better in a few hours, or if she starts coughing, acting lethargic, or has facial swelling, then she should be seen by a vet for injections of antihistamines and steroids to help with the reaction.

Also note that the wet or dry of a dog's nose just depends on their current environment and the time since the last licked it. Same thing for cold or warm! I have never included the nose temperature in my physical exam. ;)