Overwatered cactus? Cut and replant or wait?

[sleepygarden]

Hello friends!

Found this on my plant the other day:

20170523_182414-1-1.jpg (100.44 KiB) Viewed 677 times

Would you say the white spot is a splitting or mealy bug?
Some context:
1) Watered it the previous day after no water for 2 weeks (am very afraid of overwatering lmao)
2) found similar white spots on another plant I brought home recently (removed)(also how should I remove a bug from this cacti)

There's also this:

20170523_182302-1-1.jpg (64.36 KiB) Viewed 677 times

Same thing but without flash, sorry for low quality pics sighs

20170523_182240-1-1.jpg (397.92 KiB) Viewed 677 times

Is it rot?
Plus the tubule it's on seems to be shrinking :/ actually this seems to apply to many of the lower tubules

Personally I'd say it seems over watered due to the yellowing (?) (even tho it had received very little water)
If it is over watered, should I cut and replant it?
I plan to do a root check + change the soil (I got it just a little under a year ago)
Should I just wait and see so as to avoid stressing the plant?

Any help is much appreciated!!!

ps this is the least of my concerns but it doesn't seem to be growing spines at the top (it's probably a mammillaria and Google images seem to show mammillarias with spiny tops lmao)
(I'd like to upload a full picture of it but it's too big and cropping gives terrible quality + doesn't work anyway)

[esp_imaging]

You have tiny, barely noticeable blemishes. I'd ignore them, if I ever noticed them.
A root check is always a good idea with plants you are concerned about.
How long does it take for the compost to become completely dry say 2cm below the surface after watering? If it dries out quickly, only a few days after watering, it can probably take quite a bit more water. Give it several days to recover after you do a root check before watering.

[hegar]

By looking at the circled areas on your pictures, it does look like some kind of minor mechanical injury. In one case it looks like a scrape and the other seems to be an injury to the tubercle. The plant should not be impacted by either one of these things. I do get to examine a lot of cacti, that were either collected in the wild or not treated well when dug or transported. Usually, the injuries do heal quickly and no rot sets in.
Just make sure, that the tubercle spot does not grow in size, change color or become softer than the healthy looking tubercles surrounding it.
Any injury could become infected, if a pathogenic microorganism entered the plant at the site of the injury. Once a corky protective layer of tissue has formed over the wound, the plant should be OK.

Harald