I made that same mistake myself and if you read the temps on the tin it doesnt do for our high summer temps and then it lifts and bubbles in the heat and leaks in winter or during the rainfall.
But you need to clean away the damaged area first and then paint it with red, grey , green or white SEKA. Can get it from Mayors or Ive bought the grey and the white one from Paviementos in Jesus next to Clibegas.

However,if you have a crack you would be better advised to buy a small bag of waterproof concrete before you paint over it.

Going forward it is best too recover the whole flat roof with waterproof concrete and then tile it using pool tile adhesive.

Have fun with flat roofs . I have encountered every pain possible with roof issues over the last few years.

Good luck. ::)