I don't think it looks like mould rather a pellicle forming- probably acetobacter. Does it smell slightly vinegary?
It's important that you stop all access to oxygen. If you can bottle it now then do so. If you have any, add the tiniest pinch of vitamin C (ascobic acid) to each bottle. If you haven't don't worry. Rack or draw the beer off from under the pellicle- it'll tend to stick to the sides of the barrel as beer level falls. As soon as you seal the bottle, the bacterium will stop growing and multiplying. You may get a faint vinegary whiff when you reopen the bottle, but it won't spoil the beer and the smell will be pushed out by the effervescence. Don't even bother trying to cold crash it. It's important to stop the acetification.
Here are some pictures from google:
https://www.google.com/search?q=ace...KyYUKHZHcBAEQ9QF6BAgMEAE#imgrc=mjztQWnzTElTxM
Even if it does turn out to be mould, it wont harm you:
https://www.ratebeer.com/forums/white-mold-in-secondary-safe-to-drink_138483.htm