Someone using my wifi password

[Witchypoo2]

Hello.

I'm new on here and not very technical with broadband and such.

I'm a bit worried and think I've been a bit stupid but I would like a bit of advice. 

I have had two workman in today to fit a new boiler and one of them asked me for my wifi password,  I replied I wasn't sure what he meant but I'm aware not to give my banking & apps passwords and things like  that , anyway he picked my router up and took a photo of it underneath,  then spent most of the time on his phone.  I'm worried about it now that he might be able to access my data.

I feel really foolish now because I should have stopped him. Anyway they haven't finished the boiler and are coming back tomorrow. 

I have phoned my landlords and they are definitely coming back tomorrow. 

Is this usual for tradesmen to use your wifi? Am I overthinking this and should I be worried?. I did think well if he was up to no good he wouldn't be so open about it, or would he?. 

Any advice would be very much appreciated.  Thank you.

[SKY1992bf · Accepted solution]

@Witchypoo2  First thing to do is switch off the hub physically pulling the plug out for an hour this will rest your ip address

second change the WiFi password that you gave out to something different 

third change the administrator password on the hub as well 

[TimmyBGood]

@Witchypoo2 

But don't worry overmuch: WiFi credentials are only useful within wireless range (so inside the building and a few metres from it), and don't by themselves permit access to any personal data.

[Witchypoo2]

Thank you for your reply and help. I've got a new router that I haven't got round to installing yet, it's a faster broadband speed ,as I said I'm a bit tech shy so I was waiting for a friend to install it so it connects to my phone.   It has  new  passwords & codes so That will do the trick!  will put my mind at rest.... Note to self be careful what you share!. Thank you.