In our family, my mom makes homemade mac n' cheese for Thanksgiving and New Year's dinner. She always uses the Whole Milk, and that's for one reason. When you are baking, whole milk tends to be thicker than 2% milk. Using the whole milk makes the mac n' cheese more creamy. If you wanted to bake cookies and make homemade dough, 2% would be the better option, unless you want the cookies to be super soft. Personally, I prefer 2% milk, but a lot of recipes call for whole milk. If you wanted to make something like homemade cake frosting, you would use whipping cream and 2% milk. Why? Because if you used whipping cream and whole milk, the frosting would be extremely thick, and ultimately very difficult to hand mix (even if you used one of those plug-in mixers, it would still make a huge mess).
If you really can't move your arm because of the sting, and there is pus, the best thing you can do to yourself is go to the Emergency doctor. You can take an ibuprofen if the pain is too hard.