The powerful all-rounder arrived in Sydney Monday morning after tweaking his hamstring while bowling in Australia's series-deciding one-day loss to India in Bangalore Saturday.
"It's not too bad," Watson told reporters at Sydney airport.
"My body's really adjusting to bowling, it's just an unfortunate little hiccup. Being here, it'll give me a week or two to be able to hopefully freshen up and be ready to go for the first Test."
The opening Ashes Test at the Brisbane Cricket Ground is scheduled Nov 21.
Asked if he had any doubts about playing in the series opener against England, Watson replied: "I'd never say 'no doubt' but I've been able to get on top of this sort of thing over the last eight or nine months with a few niggles that I had even throughout the Ashes as well."
"So I'm very confident that things should work out OK over the next couple of days and the results will be what I think they are and there shouldn't be any problems at all," he added.