Welch has five days to respond to the penalty but will accept the fine.
“I am deeply sorry and regretful for my actions,” Welch said in a statement on Saturday.
“I’d like to thank my family, friends and the club for their support over the last couple of days. My actions have let everyone down including our amazing members and sponsors.
“I know it’s a privilege to play for this club and I deeply regret my behaviour. I fully accept the NRL sanctions and I will be doing everything I can to make up for it.”
NRL chief executive Andrew Abdo said all players and officials had to comply with the league’s protocols.
“Complying with the protocols is absolutely critical to our season. The protocols ensure we protect the safety of our players, staff and the community,’’ Abdo said.
“Any player or official who breaches the protocols will face significant fines. The overwhelming majority of our players and officials have done the right thing throughout a very challenging season. It is critically important that compliance continues.”