Why Do I Occasionally Have Blood In My Spit, Especially Since Recovering From COVID-19?

Hi my age is 30, I am getting blood in spit in the morning and sometimes in the evening. I got covid last may 2020 since then it all started, it don t happen everyday but at some intervals i see it. My recent blood test reports are normal. I have done endoscopy also to find if there is anything but endoscopy reports says the stomach is reddish nothing else. I have consulted with ENT but there is nothing significant. Cant really figure out the reason as to why the blood is coming in saliva or spit sometimes. I have hypertension and its under control with medications. Looking for help.