Getting bit is a good learning experience. Once bitten you are less likely to be so surprised that you yank the frog out of it's tank and onto the floor. Been there done that. They do have very powerful jaws so it will hurt especially if they get you with their odontoids(the tusk like projections in the center of the lower jaw).

Just don't freak out and realize that eventually you will get bitten. Also when tong feedint never offer them food with the tips of the tongs pointed towards the frog. They can accidentally impale temselves on the tong and be seriously hurt or worse. Always point the tips away.