Skin tags on bum area are common and usually benign. There could be even multiple skin tags at once. Even though they are harmless but if they're in the way, it can cause discomfort and itchiness.
Since the bum area is usually softer and looser than other body parts, heavy lifting and strenuous exercise are one of the few reasons for the skin tag. There's a lot of friction while working out that's there especially in case of women with tight leggings.
One simple way could be just taking an image of your skin tag and comparing with other skin tag images found on Google Images. But it is recommended that you consult with your doctor as well to make sure it is not a tumor or blood clot or something else. Especially if it is near the anal region. If there's a doubt, the doctor might take a tissue sample and send it to lab for testing.
If you're not having any issues with the skin tag, just leave it alone as it is harmless in most cases. But if you're experiencing any sort of discomfort then you should consider the removal.
Getting the skin tag removed from your professional healthcare is the best option. Especially if you're having pains, discomfort or bleeding on the skin tag. The surgeons use a process called Cryosurgery which destroys the cells of that tag completely, to avoid growth of cancer cells (if there were any diagnosed).
However if you want to get the skin tag removed only for cosmetic reasons, there's other OTC (over the counter) alternatives which are mostly safe. It is best to use OTC methods because most insurances will not cover the procedure due to it being cosmetic in nature.
You can simply use devices such as Skin Tag Pen by Aven Buzz and get rid of the skin tag easily right at the privacy your home.