Hi,
If the spot is there regardless of what is showing on the screen and it is always in the exact same place (even if you rotate the screen) it may be that there are "dead" pixels in the LCD display.
If you go to ''Menu > Settings > About phone > Legal information'' in your phone you should find information regarding what is covered by the warranty on your phone and hopefully some mention of their dead pixel policy.
Given that it is only 4 months old, I suggest that you verify the warranty period is still valid by checking the date of purchase on your purchase receipt, then contacting the manufacturer's customer service section (or do what is stated in the warranty document) regarding a warranty claim for repair or replacement.