It could actually be regular ol' hems.
They're often (but not always) painful, particularly if they're hard, if they're really small then maybe there won't be that much pain. It's called thrombo-something or whatever, which means that blood has kind of coagulated where there's a weakness and failure in the structure of your blood vessel (hemorrhoid). The way i understand it, two contributing factors are drinking too little (thicker blood) or inactive circulation which makes blood cells heap up, particularly where there's a weakness in the blood vessel.
Tips from experience (aside from prescription treatment):
1) Increase water intake, drink regularly throughout the day and make sure you get at least 8 tall glasses a day.
Gulp down 1 as soon as you wake up, stay on it.
2) Increase physical activity, aka keep your circulation going. I recommend just adding more walking with whatever intensity you feel comfortable with. Staying warm, taking warm baths etc. Be aware of sitting too long, change up whatever position your standing/laying/sitting in. And maybe ease up on resistance training for a while, you don't want to increase pressure in your veins when you're trying to heal.
3) Counter-intuitively, buttplug wearing often helps (it used to be the #1 prescribed treatment).
It eases the pressure in your sphincter, thus easing pain from the muscle squeezing the H.
Freer/Increased blood flow also promotes healing, pointing back to the two previous points.
And if you stretch your anal "structure", you also cause some damage to your veins that sometimes need time to catch up and heal. I think a lot of stretchers have hems all the time that don't bother them, because of the constant symptom-relief of being all loosey goosey down there, and deflating the hems by using toys that squeeze them empty etc.
I think some guys get more hems and discomfort when they stop playing.
If you are uncertain about what's up or worried you should always see a doctor.