The left-back was signed by Celtic for 25 million pounds last summer, but arrived at Emirates Stadium injured.
Tierney showed form previews in the Europa League and the Carabao Cup, but suffered a dislocation of the shoulder in December after playing only five Premier League games.
However, the 22-year-old Scottish international is back in shape and looking forward to returning to the field with the Gunners.
And, thinking about his move, Tierney admits that it was not a simple decision to leave Celtic – but has no regrets.
He said Sky Sports : “I had sleepless nights. It was a difficult decision. I knew the size of Arsenal. They are a massive club in a massive league.
“It was obviously a great offer, but I still had sleepless nights thinking,” What’s the best thing to do here? “. It lasted for centuries.
“The first offer arrived and I then signed the deadline. At the same time, I was coming back from my injury.
“I was like, ‘Don’t even focus on what’s going to happen, work hard and be in good shape, everything is happening for a reason.’
“Arsenal is a huge and massive club and when I came I realized it. “
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Last week, Mikel Arteta supported Tierney to make a good impression with Arsenal at the start of the season.
” Too bad [about his injury] but it’s still part of its development, “Arteta told Ian Wright on YouTube.
“In your career, you are going through these moments. I challenge him to say “Kieran, how are you going to react to this? ”
“You can’t feel sorry for yourself, the pressure level is now a little higher but you have to deal with it.
“You play with a high level club, with expectations, face it! You have everything to succeed here, you have the best possible attitude that I know of a player who will benefit from it. “