Read books about habit formation and apply the ideas about identifying a trigger to a habit, and altering the response. Most importantly, you can consider identifying and addressing the emotional motivation behind the habit.
I’m a fan of BJ Fogg’s “Tiny Habits” as the book includes memorable summary diagrams, and the author is credible as an active researcher (his work was cited in the lectures of a university course I later took, after reading his book on my own). Alternative books are James Clear’s “Atomic Habits” (which cites BJ Fogg’s work) and Charles Duhigg’s “The Power of Habit.” There is a lot of overlap between the ideas of each book, so you can’t go wrong, though I found that BJ Fogg’s book was the most concise.
The most relevant idea from Fogg’s book is that behaviour is a function of motivation, ability to do a behaviour, and exposure to prompts for the behaviour. From a summary of his book [1]: “B=MAP considers that there are 3 key factors that need to be present for any behaviour (B) to occur: motivation (M), ability (A), and prompts (P). The model proposes that when these three elements are present at any given time, the person is pushed above the ‘threshold’ for action to do the behaviour.”
It sounds like you’ve already thoroughly attempted to change the habit by reducing your ability to engage in the behaviour (via blocking social media). Fogg, in his chapter on changing a habit, strongly recommends addressing the motivational aspect behind the behaviour. You can consider the question: what is it that motivates you to check for emoji reactions? For example, Fogg discusses how a person fixed a sugar consumption habit once she identified that it was a response to grief from losing a loved one, and addressed her grief in a healthier way—this may or may not be relevant to you.
Prompts are also important (via asking yourself: “what prompts the behaviour to check social media?”), as Fogg also recommends using them as a starting point to change your response to a healthier alternative. But he emphasizes the importance of focusing on the motivational aspect, as he wrote that it would not have been enough for the person with the sugar consumption habit to simply replace sugar with a healthier alternative like celery—the motivational aspect was the most important for her case.
[1] https://www.habitweekly.com/models-frameworks/the-fogg-model