Period delay first time ever. And safe.

Hello respected Doctors. Greetings. Hope you and your near ones are fine and safe. Thank You for your services. My query is I am 38 yrs old unmarried female with no history of diabetes and thyroid. My HB is 13.5. My female friends and me we all got our jab first shot covishield vaccinated from our office on the. 7th Of July . My periods are always regular with my cycle days of 28 to 30. Not more than that. Last period date was 15th June. This time I got my periods today, delayed by few days with lot if cramps. I had never ever faced such cramps before. My female colleagues have complaint the same delay with higher flow n pain. I am worried and speaking for my fraternity too. What's causing this? The vaccine 1st shot. Then what will happen when we take the 2nd dose. Sorry for the lengthy query. Thnx in advance.