You may, indeed, have a burst blood vessel in your leg basically causing a bruise. The other possibility is that you have an area of eczema or even a fungal skin infection such as ringworm.
If this is not beginning to get better in the next few days I would suggest you have your doctor take a look at this. If it is a burst blood vessel it will heal on its own. If it's one of the other possible causes there may a topical treatment to help it resolve.
Advice and opinions given are based on the information provided and must not be considered an official medical recommendation. The limitations of the internet prevent an appropriate evaluation. Always consult your doctor if there is concern.