Hello,
I totally messed my retopology and I saw that error, as you can see in the first picture, after I increased the value of the multiresolution modifier to a higher value (4/5/6)
I completely overseen two vertices were not merged together which is a critical mistake at this point
As you can see after I try to merge these vertecies I get this kind of “glitch”.
How can I fix this error without losing all the details and hour and hours of work?
Few more details -> I'm still a beginner to sculpting (about 3 month experience in Blender ) and this is my very first real project that I'd like to add to my portfolio.
I suppose you'd like the original .BLEND file to take a closer look at the problem but I don't want to make it public. Could you send me a private message?
I would be glad if you also could give me some feedback on my current work as well :)
Hey Artur,
It looks like a silly bug,
Try this solution, if this doesn't fix it let us know.
Sorry, but Method 1 and 1b didn't work for me.
After the "rebuild subdivisions" step I tried to fix the vertecies problem in the "Edit" mode...
...and got this result after merging these two vertecies 
Hi AutopsyGuy this should be fixable. I've made simple mistakes like forgetting to merge verts as well. Multires is usualy robust enough to handle small mesh tweaks like this.
If you post a download link to your .blend file I'll be happy to take a closer look. The best way to do this is by uploading your file to Dropbox, Google Drive, Mega, or equivalent file hosting service then copy + pasting the share link here.