This is happening because you talked to the man in the blue shirt outside of your school in the afternoon at some point. This is a major flaw in this version of the game. This man will fix a bug later on in order to continue with Tyna's quest. However, if you talk to him too early it sets Tyna's quest variable way too high and when you walk into East Town it triggers one of Tyna's scenes. This scene should happen after a transport into East Town where your character spawns outside of her house and has room to walk.
To fix it you need to use a save editor like saveeditonline.com and edit your save file to change variable 103 to a value of zero. Or if you have done some of Tyna's quest already you'll have to tell me where you were because then it may need to be set at something other than zero.
*EDIT: technically you could walk into East Town from the left sidewalk in Commercial Neighborhood and your character will have room to walk and complete the scene. But this still isn't good because it will break Tyna's mission later on down the line. You'd still have to roll back the quest variable to Zero at some point but then you'd also have to change the event Self Switche to fix it. I know
@DuDraig can fix these but most people don't know how.