The dark spot you have described below your bottom lip is a fairly common occurrence among people who have generally dark skin to start with. But sometimes, even those with light skin can experience this anomaly. The first thing you need to know is that this is nothing to be really alarmed about. The next thing you should be aware of is that this spot may be considerably lightened over a period of time and constant care. You should try the methods mentioned here regularly and you will see results in as soon as a month sometimes. Your best bet is to gently bleach away the dark spot with natural products. This will also ensure that the spots do not return to haunt you repeatedly. Use half of a tomato to cleanly scrub out your face regularly. Pay special attention to your dark spot. Spend a couple of extra minutes scrubbing this spot. Please note that you will not see instant results. You should do this for at least two weeks, on a daily basis to see the results. The best time would be while bathing. About once a week, make it a rule to exfoliate your face. Use a gentle exfoliating scrub solution. If you like, you can make one of your own with a few sugar crystals and olive oil. This can be used to scrub your face till the sugar crystals dissolve. Regular cleansing and exfoliation of your face in this manner will also help to even out your complexion very well.
Another excellent solution is to make a paste with one almond, a strand of saffron (both soaked overnight separately) and a few drops of fresh cream. The almond can be peeled and rubbed into the cream and saffron till you get a fine paste. Apply this to your dark spot and leave it overnight. This will help to lighten that particular part of your skin and give it a gentle and beautiful glow as well. This will take time but it is a very effective and also mostly irreversible method to use. A teaspoon of fresh yogurt can also be mixed into a half teaspoon of gram flour and used to scrub your dark spot. It will help to deep cleanse the skin and get rid of the darkness as well. You can also dab on a drop of lime juice to your face every so often. This too is a natural bleaching agent.