The 15-year-old was reportedly attacked at around 3.10pm on Tuesday. The police and an ambulance were alerted to the incident by a concerned member of the public.
It is not known if the boy and his attackers were pupils at the nearby Moor Park Business and Enterprise School.
Shopkeeper Sailesh Patel told his local newspaper that residents were 'shocked' by the stabbing.
"We saw the commotion, the police and the ambulance further up the road," he said. "We heard that a young boy had been stabbed. It is a shock for the community. I have been here 35 years and nothing like this has ever happened."
The boy was allegedly stabbed by two teenagers, and was left needing hospital treatment for his injures, which the police describe as not life threatening.
Two youths of 16 and 14 have now been arrested on suspicion of wounding.
Det Sgt Peter Glover of Preston CID confirmed the boy had been stabbed, and said he was now recovering at home:
"This incident happened on St Paul's Road at about 3.10pm at the junction with Charnock Fold. It appears there has been a fight involving two on one and the victim has ended up with a minor stab wound to the back of his leg.
"No weapon has been recovered. If anyone has seen anything suspicious we would like to hear from them."
Local councillor Terry Cartwright said he was 'totally shocked' that school-age children were carrying weapons.