Question: If a person, ALLAH forbid, does gustakhee of the Prophet Peace and blessings of Allah be upon Him, Can that person repent to Allah ? Will his Taubah be accepted by Allah? Or does he / she have to be punished before their Taubah is accepted?
Answer: Of course he can repent and ask for forgiveness from Allah S.W.T.
It is a sin like other sins and just as one can repent from other sins, he can do so from this sin as well.
It is good that Allah put the thought of repenting in his heart and mind, and it is a sign that Allah want to forgive him for the mistake he has done.
Just one condition that repentance should be genuine and honest.