Hi and Welcome!
(I'm sorry that I didn't get to your question sooner. I was on vacation from the 21st-27th, and sick when I returned.)
How is your son doing now? Milestones really can affect sleep for up to two weeks. There is extra adrenaline during a milestone, which leads to more wakefullness which helps baby practice the new skill over and over again. With standing, the screaming and crying usually comes because he can't sit back down. I noticed my son was extremely agitated and excitable with each new milestone, and some babies are more affected than others. It did go away over a short period of time, and he was back to normal again.
You can lay your son down each time he's standing and let him know it's time to sleep, or you can leave him and let him work it out on his own. I'm hoping all is well now. Please post an update if you get the chance. Feel free to ask any other questions

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