My Dog Has An Anal Infection.. Advice ?

Ok Im freaking out, all the vets are closed right now and I just noticed a dog that has been s**king on my dog for awhile in the rear end area. It seems really pink with white puss along the bite marks on the skin, and the dog needlessly wont stop yelping I feel so helpless, its pouring blood out here and there every once in awhile, its so sad to see. I put some budweiser and cheese on it cause my grandpa seems to be right sometimes but also loses his mind, so I dont know if thats the best advice, someone help.