The arrests took place following a major rally that took place in Sheung Shui area on Saturday against tourists from mainland China and parallel traders, those who source consumer goods in Hong Kong for sale across the border, the South China Morning Post.
The rally finished peacefully but later descended into clashes including an hour-long standoff between police and protesters.
About 30,000 people took part in the main rally itself, according to the organisers, while the police estimate was about 4,000.
The protest was an offshoot of the movement against the now-suspended extradition bill, which would allow the city to extradite offenders from the city to jurisdictions Hong Kong does not have any extradition deals with, including mainland China, where protesters fear unfair prosecutions.
Saturday's demonstration was held in opposition to the influx of parallel traders, who bought their stock tax-free in Hong Kong to resell it in mainland China.
Residents said that led to higher retail prices along the city side of the border.
Regarding the arrest of the man who tried to jump off the footbridge, pro-democracy lawmaker Andrew Wan Siu-kin accused the police of arresting the wrong person, saying the young man was not involved in the protests but nearly lost his life, reports the South China Morning Post.
A police union hit back at Wan's "misleading" comments, saying officers had rescued the man by stopping him from leaping off the bridge.
In a statement issued in the early hours of Sunday, the police said the man was suspected of obstructing the police for advancing on their cordon and was arrested for unlawful assembly.
( With inputs from IANS )