33 minutes will not make you anywhere near last at parkrun. Check the website and you will be able to see the finishing times for every run. My local one, which is flat, often has finishers around 45-50 minutes. By its whole nature, it is inclusive, friendly and fun.
Every run is different, and the same run at the same speed in the same conditions can feel brilliant one day, and really hard the next time. As long as you are only doing a session as hard as that a maximum of once a week, and your resting HR isn't drifting (which could indicate overtraining or the start of an illness) it should be fine.
If your calves are still sore half way through your next easy session, be careful as DOMS should ease with a warm up.
Obviously if you feel light headed, sick or have chest pains - stop!