Stimming and distressed

Thanks 

Just be honest is best but I don’t talk too much about it as that will make him very anxious 

OK.  That would suggest that there isn't too much to be concerned about in relation to your son's behaviour.  If he is anything like me (possible, but unlikely) I am always calmer when I know exactly what the situation is regarding someone's health.  Perhaps keep your son in the loop regarding granddad's health....in age appropriate language.  Shocks and surprises upset and unsettle me......sad, tragic or uncomfortable realities do not bother me half so much...so long as I know and understand about them.

Good luck.

Yes I have some ideas, mainly around changes and things being different from usual., We have the six week holiday, he misses school and he hasn’t seen his Grandad for weeks and he sees him regularly, his Grandads in hospital. 

Hello 75657, I am Number.

I think it would be really helpful (and potentially important) to understand what was different in your son's world last night.  If the running normally calms him - but last night it did not - then I presume something was different/worse for him.  Whilst asking him might deliver the answer to this, I think it is more likely that you will have more success if you wrack your own brain.

I wish you luck.

Thank you usually he’s stimms calm him but not last night 

The following books should give you a lot of background info as well as practical advice on how to idenfity, manage and prevent the anxiety build ups that are happening, but also what to do when they go from building up and into meltdown.

Managing Meltdowns and Tantrums on the Autism Spectrum - A Parent and Caregiver's Guide - Jenna Ward-Hawkes, Melissa Rodi (2019)
ISBN 9781785928406

Managing Meltdowns - Using the S.C.A.R.E.D. Calming Technique With Children and Adults with Autism - Deborah Lipsky, Will Richards (2009)
ISBN 9781843109082

You know him best so will ultimately be able to fine tune any approaches to the issue, but importantly you can teach him how to do it for himself when at school and eventually in life away from home one day.

Good luck and please come back for advice or even just chat when you want to.

He’s seven. Thank you for your help 

What age is he?

To help you need to focus on the root cause of the anxiety rather than the stimming behaviour itself.

I suspect something was making him extra anxious which led to the increased levels of being upset. Work out what that is and you have a good chance to deal with it and prevent a recurrance.