"Mr Sandoa was attacked by the goons of mining mafia," AAP senior leader Sukhpal Singh Khaira, who is also the leader of opposition in Punjab assembly, said.
He said the legislator was rushed to PGIMER at Chandigarh.
The AAP legislator's turban was tossed up during the attack and two of his security personnel were also thrashed.
"If this is the plight of the elected representatives who have been provided security, imagine the fate of ordinary citizens," Mr Khaira told news agency PTI over phone on his way to see Mr Sandoa at Chandigarh.
The latest incident comes three days after two employees of the Punjab's forest department being attacked by the sand mafia. Four officials had escaped with minor injuries.
Two officials including a forest officer were brutally thrashed by five to seven assailants with sticks and sharp-edged weapons on the night of June 18 when they intercepted a tractor-trolley near Seonk village in Mohali.