Look like you create a procedure and then try to execute it from SQL*Plus.
The schema name of the procedure should be your login name when you create the procedure.
If you still use the same login name to execute this procedure, there should be NO problem.
But, there will be a problem if you use a different user to execute this procedure under the condition that you didn't grant execute priviledge to the new user.
Just some thoughts, may need more detail to troubleshoot your problem.