can't access my wp-admin

Hello,

I’m new here and I want to apologize if a similar matter exists in this forum (in that case if you have a link to help me I would be happy!).
I have updated my WordPress today but it doesn’t work.
After updating I did the logout but then when I tried to login again I have this error:
Warning: Cannot modify header information – headers already sent by
It also tells me that I have to accept cookies but I checked, it’s ok.
I guess I updated to the latest version… I just can’t check because I have no access…
How can I do to access my website?
Thank you,

Emilie