I have a horrible problem with needles. I don’t mind my own blood or having holes stabbed into me or even having a doctor fishing around in a dime sized hole in my arm looking for bottle cap fragments (long story). But needles freak me out like nothing else. I always warn the doctor that I’ll faint and to just give me the injection/take the blood while I’m out. But they never listen, they wake me up and pick up the needle and out I go again, this repeats until the doc gets disgusted and just does it my way. I hate needles 
I work in an office where we give PPDs (TB skin tests).
It’s really not a big deal. It’s just subdermal, not into a vein or a muscle. There is absolutely no reason AT ALL for a tourniquet or ball. If they’re having you do that, it’s not a PPD. Ask for information about the shot - the nurse, if he/she is a good one should be happy to talk to you about it and put you at ease.
Tell the nurse beforehand that you’re having problems with needles lately. Our nurse always asks so that we can have the person lie down if there’s a risk of fainting so you won’t hurt yourself.