Door lock does not work from the outside after I replaced door handle

My door handle broke which happens often as they are cheep plastic parts so I decided to learn off you tube to fix it myself. I got a new part and installed it but somewhere in the process I must have bumped the door lock mechanism and something came loose a person from inside the shop where I bought the part came to see if I was okay and knew what I was doing and I said yes I know what I'm doing with the door handle but I don't know what I did to the lock he did something to which looked alright at that moment and he went. I eventually assembled my door handle and door and saw it all was working good but later found out that I could not operate my door lock with the key any more. Can you please advise me on what I should do and how to fix this problem and if there are any videos online to show me how to fix this myself.