Ignore it. Start afresh with a new ‘16th’ Doctor. Then later on, throw in a line like -
‘The regeneration process is a bit messy. Sometimes I get sick or lose my memory. Once I turned into an old friend of mine for a few minutes before settling on my final form.’
Done.
Dr Who is Rose Tyler
The Master is a tooth
Susan doesn’t exist yet
Rogue is in hell
Belinda has been lobotomised
Ruby was abandoned again
The Rani was eaten by Absolute Omega
Where do you go from here tbf