How do i fix this i pressed R by accident

[Persuasiv]

https://ibb.co/bMh9nS9w

When i was editing i pressed r

[rich2005]

(Yesterday, 09:14 AM)Persuasiv Wrote: https://ibb.co/bMh9nS9w

When i was editing i pressed r

....and....what ? You got the ForeGround Color Picker using r [R] That is not standard. 

Here is a list of (most) keyshortcuts https://docs.gimp.org/quickreference/gimp-keys-en.pdf

and R default is the Rectangular Select tool.      

Have you have changed the defaults ?
You can reset using  Edit -> Preferences -> Interface -> Reset Keyboard Shortcuts to Default Values