He put on perfume after doing ghusl and donning the ihram garments; what should he do?

Praise
be to Allah.

Putting perfume on the head and body at
the time of entering ihram – i.e., after doing ghusl and before forming the
intention of entering ihram – is Sunnah. That is because the Prophet
(blessings and peace of Allah be upon him) put on perfume for his ihram. It
was narrated that ‘Aa’ishah (may Allah be pleased with her) said: I used to
put perfume on the Prophet (blessings and peace of Allah be upon him), using
the best perfume he could find, until I could see the glistening  of the
perfume on his head and beard.

Narrated by al-Bukhaari (5923). 

 What is meant by the glistening is the
shine of the musk in the parting of the Prophet’s hair when he (blessings
and peace of Allah be upon him) was in ihram. 

If the cream that you put on your body was
after doing ghusl and before forming the intention of entering ihram and
beginning the rituals, then you do not have to do anything, even if you had
already put on the ihram garments. 

Rather what is prohibited is to put on any
kind of perfume after forming the intention of entering ihram. 

But if you did this prohibited action out
of ignorance, not knowing that it is prohibited to the pilgrim in ihram, or
you had forgotten that, then you do not have to do anything either, but you
have to remove the traces of this perfume as much as you can. 

Shaykh Ibn ‘Uthaymeen said: If a person
does any of the actions that are prohibited when in ihram, because he forgot
or was unaware of it, he does not have to do anything, but as soon as that
excuse ceases to be applicable, he has to stop this prohibited action.

End quote from Fataawa Arkaan al-Islam
(536) 

See also the answers to questions no.
36522 and 49026

But if you put the cream on after you had
formed the intention to enter ihram and start the rituals, knowing that this
action was one of the things that are prohibited, then you must offer a
fidyah, which is one of the following options: either sacrifice a sheep, or
feed six poor persons, giving each one half a saa‘, or fast three days,
because Allah, may He be exalted, says (interpretation of the meaning):
“and do not shave your heads until the Hady reaches the place of sacrifice.
And whosoever of you is ill or has an ailment in his scalp (necessitating
shaving), he must pay a Fidyah (ransom) of either observing Saum (fasts)
(three days) or giving Sadaqah (charity – feeding six poor persons) or
offering sacrifice (one sheep)” [al-Baqarah 2:196]. 

See: Majmoo‘ Fataawa Ibn ‘Uthaymeen
(22/110) 

With regard to putting perfume on the
ihram garments, that is not permissible, whether that is done before
entering ihram or afterwards, because the Prophet (blessings and peace of
Allah be upon him) forbade the pilgrim in ihram to wear any garment to which
perfume has been applied. Shaykh Ibn ‘Uthaymeen (may Allah have mercy on
him) was asked about perfuming the ihram garments and he said: It is not
permissible, because the Prophet (blessings and peace of Allah be upon him)
said: “Do not wear any garment that has been perfumed with saffron or
wars (a plant dye).

End quote, Majmoo‘ al-Fataawa by
Ibn ‘Uthaymeen (22/9) 

And Allah knows best.