Have you determined your max heart rate (HRM), and if so, how?
HRM is highly variable among individuals and calculators based on age etc are a waste of electrons.
If you know your HRM (and if you're not puking while finding out, you're not there yet) you can calculate your heart rate reserve which is the difference between resting and max.
I'm a 60 year old runner. Speed work and tempo sessions will put me up in your range for up to 30 minutes at a time. Interval work will put me over 90% for a couple minutes with a minute or two of cooldown between peaks.
Generally it's not a problem. Your body won't let you work hard enough to damage it (lots of caveats here from cross-fit people who somehow manage to develop rhabdomyolysis). You will develop loss of willpower/overwhelming exhaustion before you can work to your limits. If you are just getting active then yes you can injure yourself easily, but probably for different reasons.
Big caveat here You can train to ignore your body's signals. Cross-fitters do it, free divers do it, endurance swimmers do it, and lots of others. If you are one of those people you can absolutely hurt yourself to the point of death. But if you are not explicitly training to ignore your bodies safety signals you should be fine.