Hi Mari, welcome to the forum.
What you describe is perfectly normal. Almost everyone who undergoes an ablation experiences an elevated resting heart rate for many months following the ablation. And when I say elevated, I mean the upper 80s and 90s, not over 100. This elevation can last a surprisingly long time, sometimes a year or more. It's perfectly normal, to be expected, and utterly harmless.
Should you be riding your stationary bike? Absolutely yes! Crank that heart rate up and go for it. Your ablation didn't make you fragile. It made you stronger so go for it.