Should I Tell My Girlfriend Her Ex Started Liking My Instagram Posts? Also What's He Trying to Get At Here?

Early into dating, my girlfriend told me about a guy she was seeing that still messages her every few months to "check in" -
She started dating him back 2019 however he already had a girlfriend and didn't tell her until 6 months in. He claimed he was leaving his girlfriend, but that went on for another month. Once his actual girlfriend found out about them, he broke up with her and they stopped talking for a while. I met my girlfriend in 2021, so asked why after 3 years she's still responding/friends with him after he did that to you. I mentioned that I can't be serious with someone who still talks to ex's since my last girlfriend of 4 years was cheating on me with her "just a friend ex" - I really can't just trust someone blindly. She said she would stop talking to him out of respect for me.

Fast forward a month ago, we were on her phone watching videos together and I saw a notification from him. My heart sank and I got very upset -. She apologized, cried for making me upset and blocked him right there - claiming she doesn't respond to him for months but he keeps messaging.

Today I'm getting getting notifications that he's liking my Instagram posts (we do not follow eachother).
Should I block him too? Tell my girlfriend or will that cause drama? He's clearly trying to make a point that he knows she blocked him, but like, who cares?

Just looking for insight
Should I Tell My Girlfriend Her Ex Started Liking My Instagram Posts? Also What's He Trying to Get At Here?
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