Thanks for choosing HCM.
You have a worm infestation which needs to be treated with anti-helminthics[de-worming tablets], which may be repeated after 2 weeks.
The small lump in anus could be a external haemorrhoid / a polyp / sentinel pile.If it is painless you may ignore it for the time being.If it increases in size / bleeds then consult a Surgeon.
All the symptoms will be gradually eased by 2 weeks. You may apply calamine
lotion on arms where rashes have come.