I have the same thing. I would suggest to use cortisone cream you can buy over the counter a few times a day for a couple of days.
Mine goes up and down. I also have a fissure, plus UC. Nothing like being preoccupied with one's butt.
It's good you checked, what you're describing is an external hemorrhoid. A warm sitz bath helps to makes it feel better. The cortisone helps mine, and if it's really bad, I use the prescription Proctosetyl. Anusol is another option....I don't use any into the rectum, just apply it externally after washing.
Straining bms, extended periods of sitting/standing and not enough fibre in the diet can exacerbate them. Softening and bulking the stool with a soluble fibre supplement like Metamucil would help. Also, drink enough water and incorperate more physical activity (the "e" word
Hope you feel better soon,