Help urgently

I genuinely don’t know how I missed this but on my details of education I accidentally put my mode of education as online during my time in high school from GCSEs to alevels when I studied in person and i don’t know what to do I’ve already sent of my application

This will be one to call and ask UCAS about, I don't think you can amend mode of study once the application has been sent off.
Is your app definitely with your uni choices, or has it been sent to your school to complete?

Yeah unfortunately I sent it off last Friday
I was so sure I checked all the details before sending off, do you know what ucas could and since I made this mistake will it affect my uni application chances
Thanks for replying

I don't think it will make any difference tbh. In a worst case scenario your uni choices might contact you to clarify. But they will be more interested in the qualification than the mode of study.
Have a quick word with UCAS, they may encourage you to email your choices just to explain.