Being a 24 year old, the tooth which you told to have fallen out would have been a permanent tooth. I am sorry to say a that another permanent tooth will not grow into the space in this age. But there are various treatment options available to replace the lost tooth, starting from removables, resin bonded filling tooth, bridges, implant are to name of the options. Kindly consult your nearby dentist discuss the treatment options and have the best treatment done for you.
Scaling or tooth cleaning is required. Until then the gingivitis will not go.
Consult a dentist and take the scaling.
Then consult for proper homoeopathic treatment. To make the gums strong.
Also start vitamin c and use homoeoapthic toothpaste heclalava.