The question doesn't say what the source of the original image of the tattooed person is. That image will be protected by copyright, unless it has been released under a permissive license, or is old enough that copyright has expired (unlikely), or has lost or never had copyright protection for some other reason (possible but also unlikely). In the absence of any indication that any of these are true, this answer assumes that the image is fully protected by copyright, and that no permission to reuse or modify it has been granted.
Creating a modified version of the image is the creation of a derivative work, which is at least a technical infringement of copyright. But if this is done only for personal use, it is very unlikely that the copyright holder would ever take action on the matter.
If the screen captures are designed to show the editing process, are accompanied by comments on that process, and show only a small part of the original image (focusing on the section being edited), and if no commercial use is being made of them, then it is likely that they would fall into the "fair dealing" exception to copyright under EU law, and would fall into the "fair use" exception if US law applied.
If the above assumptions are not correct, then the screen captures might or might not fall under "fair dealing". This is a specific, fact-based determination, and no one can make it with assurance without the specifics of the images involved.
Even if the screen captures do not fall under the "fair dealing" exception to copyright, the copyright-holder might well not choose to take legal action. But that is a matter of the holder's choice. The holder would be entitled to sue if he, she, or it chose to do so. The holder would also be entitled to file a complaint with youtube. Youtube makes its own evaluations of such complaints, and can close accounts for what it judges to be violations of its policies, including copyright infringements. This is not a court or legalistic process, and the host service may not offer a chance for a defense. It can restrict or cancel an account, or take down specific content, whenever it sees fit to do so. It generally acts only when a complaint has been filed, but it need not wait for a complaint if a possible violation comes to its attention.