I would like to add that having red skin, or blisters, can become very serious. They are the beginning of a pressure sore (aka, bed sores) which you want to avoid at all costs.
When I first started with CPAP on April 2nd, it took only two nights for serious looking blisters to develop on the top of my nose because of a poorly designed (for me) nasal mask. Since it was Saturday morning by the time we realized the situation was getting worse quickly, the DME was closed for the weekend. So we went to a medical supply store to buy a couple things that may have helped until Monday so I could get to the DME to get a nasal pillow mask. Both the medical supply owner and the DME supplier were stunned how fast the sores had developed and were very obviously concerned. A couple more days without intervention would have created a serious medical problem that was probably more dangerous than the apnea that I was trying to stop.
If you would like a mask liner that will not slip out of position, try the Padacheek mask liner for your particular mask. Google Padacheek products and look for mask liners. They are not cheap but they are good and have a built in nose protector. They last for a fairly long time.
I had a severely broken nose years ago which makes the weight of the mask hurt like hell, even now. After trying 4 different asks, I love the Mirage Liberty. It covers only your mouth (for us mouth breathers) and has two nasal pillows that rest in your nose. Nothing on your nose and makes wearing glasses easier too.
I have a blister developing, but on the right side of the nose. Not sure why I am getting one only in this area as I would think if the mask were too tight I would get a blister on both sides of the nose. Maybe I'll try putting a band-aid under the mask in the area. If I loosen the mask I tend to get leaks and higher AHIs.
I posted this in another thread, but I'll mention it here since it seems relevant. I find band aid brand fingers and toes blister gel guards protect my nose quite well. I think the box just says toes now but the dimensions are the same as fingers and toes. They are thick and comfy and really do feel like a second skin. I have also used them on my feet for hiking. The adhesive is very strong and I've actually been thinking about using them on clothes before putting them on my skin to make early removal less of an event. Sometimes I just leave them on for days since they are designed for multi day use.