The 36-year-old, who will leave the Blues in the summer, scored the opening goal on a night of celebration for the Premier League title winners.Chelsea host Sunderland on Sunday in their final league game of the season.
"I've not ruled out Sunday being my last game and retiring from football," he told Sky Sports.
"If the right offer comes along I will sit down and consider it with my family - whether that's here or abroad.
"Genuinely I haven't made any decisions yet and I'm evaluating all my options at the moment.
Former England captain Terry announced last month he will leave Stamford Bridge after more than two decades at the club.
The central defender is the Blues' most decorated player, with this season's title triumph earning him a fifth Premier League winners' medal.
He has also helped them win five FA Cups, three League Cups, the Champions League and the Europa League.
The Londoner has made 716 appearances since his debut in 1998 - 579 of them as captain.
Chelsea manager Antonio Conte, who restricted Terry to a bit-part role on the pitch this season, paid tribute to the player's influence.
"He is a great man. He helped me a lot in my first season. He had a fantastic role on and off the pitch," said the Italian.
"I think against Watford he showed he can continue to play. I'm pleased for him, he scored a great goal.
"I'm looking forward to seeing him lift the cup on Sunday. He deserves this."
'I couldn't have written this farewell'
Chelsea wrapped up their sixth English title with a win at West Brom on Friday, and the home fans were in a celebratory mood as they welcomed the champions back to Stamford Bridge.
Terry, in what may be his final playing appearance at the stadium, lifted the atmosphere even more when he opened the scoring after 22 minutes.
Watford threatened to dampen the occasion with a gutsy fightback before substitute Cesc Fabregas earned a thrilling win for a much-changed home side.
The Spaniard's scuffed strike sparked joyous scenes among the home fans, while a fireworks display outside the stadium followed the final whistle.
The Blues will be presented with the Premier League trophy when they host relegated Sunderland on Sunday.
"If I could have written my story, this is how it would panned out - to go having been crowned champions, and to leave the club in great hands with the manager, the owner and the players we have here," added Terry.
"It is going to be sad and emotional for me on Sunday because I've been here 22 years.
"But I'm delighted for the experiences and opportunities I have been given."
