It's a bad idea to have space characters in table and column names. In your SQL query you apparently have a column called "Patient ID". It should probably be "PatientID", but if you insist on keeping this column name with a space in it you MUST specify the column name in all SQL statements with square brackets:
DELETE FROM PatientInfo WHERE [Patient ID]=@PID"
Oh, and just because you only have one parameter in the DELETE query, that does NOT mean you can get away with string concatenating the Id on the end of the query. ALWAYS, ALWAYS, ALWAYS use parameterized queries, even if you're only using one parameter.