I'd follow my plan that I laid out before I bought it.
My IPS for something like that was that I never let any stock get above X% of my net worth. For my temperament, I set X% to 4%. So if something got to 5% before I noticed, I'd sell some to get back down to 4% or less. Any cash raised would just cascade down to the next goal, whatever that happened to be at the time.
I don't pick individual stocks, and I don't do active management, so I never ended up in your situation. The only reason I had the rule in the previous paragraph was because I ended up with my employer stock at two different companies and had to determine how much was too much.
If it were a company that were not my employer, then logically it would make sense to allow it to go somewhat higher than one's employer stock. There are rules of thumb out there that you can google. Interestingly, when I did that research, I found two things:
1. The rules of thumb were vague and covered a range: "You want to hold 5% to 15% of your employer's stock" - OK, 5% to 15% of what - net worth, assets, investable assets, stock allocation portion of the portfolio? What would make one lean towards 5% or 15%?
2. The rules of thumb were more generous (i.e., higher percentage allocations - like 10% to 20%) when the stock market was going well for several years. Then a crash or recession happened, and the rules of thumb became more conservative (like ~5%). Incidentally, the rules on the size of emergency fund followed a similar path from more aggressive to more conservative after the recession/crash.