I'm no developer, but I remember that there's a certain link syntax for switching apps. That, plus some PHP to include your wordpress post should do the trick (I hope). A quick search turned up some articles to echo this.

For example, if you have the Facebook app and you're reading this on an app-based device, then you can hit this link fb://profile and it should switch to the FB app. So maybe there's a "telegram://message" kind of link?

As a side note: my gripe with some of the sharing buttons for messaging apps is that you can only use it via starting a blank/new message and then type the recipient. At that point, it's just as useful (if not more useful) to copy the link you want to share and then paste it into the conversations you'd like to share it to. Or... if there was a step in between that allowed you to choose which contacts and via which app you'd like to share, and it would go off and send the link separately to those individuals. Especially if I'm in a group chat, I end up cutting the link from the blank message, going to my list in Telegram, opening the group, and pasting it in there.

tl;dr