How old are you?
Was there any injury there?
Do you have any vaginal discharge?
Since when is this?
Did you notice any change in local use of either a soap or different undergarments?
Thank you for the information.
The cause for the swollen hood could be either injury(as you pulled it a little) or even an allergy(as you did use a different soap) or a yeast infection(more likely as there is itching).
You could try using Lotrimin locally to get relief from the symptoms.If you notice any redness there it could be an infection setting in and so you could need to use an antibiotic like Neosporin.
Try and avoid touching it.If the itching is very severe you could take either Allegra or Cetrizine(10mg).To decrease the swelling,try local ice(in ziplock bags)Also avoid the soap.
In case these don't offer relief and the swelling increases you would need a Clinical examination.
I hope this helps you.