Tip: How to correct a message already sent?
This is probably a feature that Twitter users would dream of having: being able to correct a message after posting it. With Telegram, you no longer have any excuse to correct your spelling, grammar, syntax and tutti quanti errors after sending a message.
To correct an error in a message, press and hold down the message and press the pencil icon to Modify it. You will only have to correct your mistake and validate your modification for the message to be corrected in the conversation.
Source : 01net