The in-form playmaker picked up the injury in last weekend's 4-0 FA Cup victory over QPR and was absent for Saturday's 2-0 Premier League triumph at home to Norwich City.
Barkley has been in fine form this season, with four goals from 21 appearances in all competitions earning him his first senior England cap - but Martinez will likely have to make do without the 20-year-old for the time being.
"Ross Barkley had a knock on his toe and we're going to assess him, but it looks like he's going to be out for a while," said the former Wigan Athletic boss.
"It could be (broken) and that's what we're worried about. It's a very similar incident to the one Leighton Baines had.
"Before we say what it is, we're going to have more scans but the fear is it's a fracture.
Martinez was wary about placing a timescale on the midfielder's recovery, but confirmed Barkley will join the club for their warm-weather training camp in Tenerife this week despite the problem.
The Spaniard continued: "Sometimes these fractures, if there is no displacement and they settle straight away, you can play straight away.
"Some can go a couple of weeks and others a bit longer like Leighton. Because it was a bad one it took six weeks.
"Knowing Ross, being a young man, hopefully we'll take him for some sun with us and some Vitamin D intake can accelarate the process, but it’s difficult to tell yet."