Talented middle-distance runner Adam Ingram also admitted separate offences of defecating in a police cell and taking a car without the owner's authority.
Belfast Magistrates' Court heard how the 20-year-old had been a "brilliant" athlete whose life is now at a crossroads.
Ingram, of Deacon Street in the city, was charged with having a bladed article in a public place.
Prosecutors said three knives were discovered secreted between his buttocks after he was arrested and searched by police on 29 March.
The taking a motor vehicle without consent related to an incident at a party in February.
A third charge sheet before the court of criminal damage involved defecating in a cell last week.
Defence lawyer Seamus Leonard set out how Ingram's problems were linked to a family bereavement and drugs issues.
"This man is really at a cross-roads; he was a brilliant runner," Mr Leonard told the court.
Ingram was said to have been part of Irish training camps, held an 800 metres record at his level, and been under consideration for a future major championship.
"As for the knives - they were bought in the city centre and he can't explain that at all," Mr Leonard added.
"They are linked to drug and alcohol consumption."
Giving the defendant credit for his guilty pleas, District Judge Fiona Bagnall imposed concurrent two month prison sentences for taking and driving away and possession of bladed articles.
Ingram was given one month for the criminal damage. It will also run alongside the other sentences.
All of the jail terms were suspended for 12 months.