Warlock: I need to clean up my campaigns in the holes of the second half.

Why reconnect it?

As he said, things have already happened and now they are part of the history of his group. Why change what happened in the past? Just as you decided to include that curse from a narrative perspective, could not you find a way to eliminate it in a similar way?

How was this curse acquired? Why would the character want to stay cursed? If the player agrees that wild magic should disappear, could not his character (and, hopefully, the rest of the group) undertake a quest to eliminate the curse?

The fact that the affected character is a sorcerer makes this even easier. If wild magic comes from your Pattern, why can not you just eliminate it? Maybe it's no longer fun and / or useful for them. Maybe the curse is interfering with the employer's objectives (the sorcerer is a little less reliable now that anything can happen around him). Can not you order the warlock to find a way to eliminate the curse? Maybe threaten to stop giving him powers if he does not make this a priority?

Everything I see is an opportunity for a great search! You said you wanted to take this seriously and make it more fun. Why not start there?