"It was a bit of a surprise when I was called up," Matthews told BBC Wales.
"Obviously I'm excited to be part of the team and it will be good experience for me.
"At the start of the season I didn't expect to play as much as I did but I've been helped by injuries to others," said Matthews.
"I think I've taken my chance and played quite well in the games I have played.
"Then on Monday morning I went in to the physio and Dave Jones called me into his office and said I had been called up.
"I don't think it has quite sunk in yet and hopefully I can keep it going. I was just happy to be part of the squad.
"If I'm lucky enough to play I will be very happy and it will be extra special to play at Cardiff and all my friends and family will be there. "It's what every footballer wants is to represent his country and do the best he can."
Matthews could still join the U21's for next weeks qualifier away in Sarajevo against Bosnia-Herzegovina.
"I haven't played for the U21s yet so I was very surprised when I got called up (to the senior squad)," he added.
"I'm not sure if I'm going away with the U21s yet - I will find out after but hopefully I will go.
"It's a qualifier and the U21s are doing well and hopefully I can go and help the team qualify."
