Praise be to Allah.
If a person has an erotic dream but does not see any maniy, he does not have to do ghusl, according to scholarly consensus. If he sees maniy but does not remember having an erotic dream, then he has to do ghusl, according to scholarly consensus. What counts with regard to ghusl being obligatory is the presence of maniy or traces thereof.
If you checked your clothes and did not find any trace of maniy, then you do not have to do ghusl just because you noticed the smell of maniy. A similar smell may be detected on clothing after sweating.
It was narrated that Umm Salamah said: Umm Sulaym came to the Messenger of Allah (blessings and peace of Allah be upon him) and said: O Messenger of Allah, Allah is not too shy to tell the truth. Does a woman have to do ghusl if she has an erotic dream? The Prophet (blessings and peace of Allah be upon him) said: “If she sees water (a discharge).”
Narrated by al-Bukhaari, 130; Muslim, 471
It was narrated from Abu Sa ‘eed al-Khudri that the Prophet (blessings and peace of Allah be upon him) said: “Water (ghusl) is for water (maniy).”
Narrated by Muslim, 518.
It was narrated that ‘Aa’ishah said: The Messenger of Allah (peace and blessings of Allaah be upon him) was asked about a man who notices some wetness but does not remember having an erotic dream. He said, “He should do ghusl.” He was asked about a man who thinks that he had an erotic dream but does not see any wetness. He said, “He does not have to do ghusl.” Umm Salamah said, “O Messenger of Allaah, does a woman have to do ghusl if she sees something like that?” He said, “Yes, women are the twin halves of men.”
Narrated by al-Tirmidhi, 113; Abu Dawood, 236; classed as hasan by Shaykh al-Albaani in Saheeh Abi Dawood.
An-Nawawi (may Allah have mercy on him) said: Ibn al-Mundhir narrated that there was consensus on the idea that if a man sees in his dream that he ejaculated or had intercourse, but does not find any wetness, then he does not have to do ghusl. And Allah knows best.
End quote from Sharh al-Muhadhdhab, 2/161
Ibn Qudaamah (may Allah have mercy on him) said: If he dreams that he ejaculated but does not see any maniy, then he does not have to do ghusl. Ibn al-Mundhir said: The scholars from whom I learned were unanimously agreed on that. … But if he wakes up and sees maniy, although he does not remember having an erotic dream, then he has to do ghusl, and we do not know of any difference of opinion concerning that either. End quote from al-Mughni, 1/130. See also Fath al-Baari by Ibn Hajar, 1/389
And Allah knows best.