The 24-year-old told Dutch talk show Matchday that he played through ankle and heel injuries as Arsenal progressed further in the Champions League.
He also revealed that Mikel Arteta was fully aware of his problems and ricked making it worse by playing him in the two legs against eventual champions PSG.
Timber has since undergone surgery to address his ongoing issues, leaving his pre-season in serious jeopardy.
He said: “It got worse and worse. I had an Oranje scan, and the conclusion was that I had to undergo surgery at the end of the season.
“I wanted to play at Arsenal, but it was hard. Sometimes the pain is much worse. I’ve been through how that feels now. I only trained one day before the match. I thought I have no idea how to finish this, because I couldn’t even run.
“But in the second half I got adrenaline again and in the 80th minute, it was time to get out. I didn’t train all those weeks and was stressing for that second semifinal.
“It hurt so much. The manager thinks: ‘Jur has had a scan, it can’t get worse, make sure you’re ready’, but he doesn’t see how much pain I’m in.”