Firstly, try not to describe your nibbling habit in such a negative way. The stinging and bleeding is uncomfortable and inconvenient but it is not a very big deal in the greater scheme of things. Try to reframe how you think about this habit.
I agree it's likely due to stress and has become a bit of a habit but most people have unhelpful habits at least occasionally, it's really not that unusual.
Think about what is bothering you in your life at the moment and if you have got over the pandemic and all the stresses you experienced then. I firmly believe that many of us are still negatively affected by what has happened over the last 2 years, it's been so mental.
Just be aware of the nibbling, don't judge it. Try some visualising: imagine, as often as you can, that your fingers are completely healed and the skin looks healthy. Then try and not nibble your nails for one short period of time and increase the time of the course of a week. Set the alarm first for 30 min, 60 min, 90 min, 120 min and try and evening, a day etc. If you bite, just start over.
Another option, which may sound a bit wacky, is to try 'tapping', google tapping their are a few key points in the body, which you are supposed to tap on whilst saying something like 'even though my nails are bloody I completely accept and love myself', rinse repeat. If there are situations where you are more likely to bite your nails, try to avoid these situations for a while.
This is quite informative
www.vox.com/2015/4/22/8464365/nail-biting
Apparently nail biting helps even out our emotions. When we're bored, it provides stimulation; when we're stressed out or frustrated, it provides a temporary calm.
Recently psychologists have come to a more plausible theory of nail biting: that it can provide a temporary escape, distraction, or bit of pleasure or relaxation for the biter.
Penzel points out that many people get the urge to bite when they're understimulated (i.e., bored) or overstimulated (stressed out or excited). "When they're understimulated, the behaviors provides stimulation, and when they're overstimulated, it actually helps calm them down," he says. Like nicotine, the idea is that nail biting can have a biphasic effect: it can stimulate under certain conditions and relax in others.
People had a higher urge to engage in the behavior in the stressed condition and the bored condition, much more than in the relaxed condition," Roberts says. Other surveys of nail biters and hair pluckers have come to similar conclusions. "It seems fairly clear that there's some emotional regulation involved.
Maybe we just bite our nails because they're there. Psychologists believe that you can get psychologically (not chemically) addicted to pretty much anything: any activity that provides a reward can reinforce itself over time.