I feel a soft lump at the back of my mouth like my gum has been pushed up. if i touch it with my finger i feel what im sure is a tooth, it seems in line under the gum and has a ridge. could this be a wisdom tooth? how long could it take to come?

You should see a dentist to find out if this is a wisdom tooth. The dentist will likely take X-rays to find out the exact position of the tooth and to find out if it is a tooth. If it is a wisdom tooth that is positioned to be harmful to the alignment of other teeth, it may need to be removed. If it is something else, the treatment may be different depending on the diagnosis. So, see your dentist.

Rule of thumb: All pain and/or bleeding and/or (as in your case) swelling deserves immediate evaluation. Probably erupting 3rd molar, but there are a myriad of other possible causes. If it has been longer than 6 months since your last oral examination, you are overdue. After examination/x-rays your Dentist should be able to give you knowledgeable personalized answer rather than broad generalities.