can we see the whole plant ...

looks like mechanical damage to me .... based only on these pix ...

ken

HU-866...

could be as ken said. or it could be oedema, or even fungal disease (I wouldn't think so...) Do not try to scratch off the scabs, it will cause more damage & they heal over again, causing more scabs. If nothing comes off when wiped, leave it alone. It they were bugs, they would have died when you used ra on q-tips. Often, it starts with rot/root rot. In case of fungal disease, a fungicide is best to use - but try to determine what it is. It shouldn't be treated with inapropriate treatment...

maybe not the best pictures, but it's an old cactus and the dots apeared not that long ago, it started to loose some leaves and look a little sad, we are planing on changing the soil this spring, but it's still winter here, so don't know if it's the best to do it now

HU-866...

your plant looks nice & green, and leaves are plump. In 1st photo, I THINK I see some dark segments - not the corking! - but not sure. Also, bottom of the pot is quite stained, & that suggests to me prolonged periods of time standing in too much moisture. I could be wrong, but if correct, the roots could be damaged. That could signal begining of root rot & may cause the leaf loss...Plant will likely take some time to recover after repotting, so be prepared. I think pot is large, & wouldn't use bigger. Could be wider (or the same size), but if, than shallower. And remember: these are epithypic plants that need very good drainage.