You can always make an updated post about yourself but it's not a good idea to use the #introduceyourself tag for it. One, it will confuse the followers. Two, it will make your profile look spammy. The best solution is to write a new post and somewhere in there link to your original one. Kind of how witnesses write update posts. Good tags for the post you're describing would be #update #thankyou #anniversary #followers and anything that the post will talk about. If you write about a specific topic such as medicine, for example, you can use that tag.