Error with headers since installing jcrecapcha

I installed jcrecapcha and then got this error:
Warning: Cannot modify header information – headers already sent by (output started at /home…….
when i tried to deactivate jcrecapcha it would not deactivate. since my website was no longer working (this error appeared to end-users also), i deleted the plugin. this has my website working again BUT when i go to the admin panel i still get this same error even though this directory no longer exists. i have reflushed my cache but something is still not right.
please advise how to resolve this.
kind regards

https://ww.wp.xz.cn/plugins/jc-recaptcha/