The UK has left the EU on the 31 January 2020. There will now be a transition period until 31 December 2020. During the transition period there will be no changes in practice for citizens and businesses on both sides of the Channel.
As a Swedish citizen living in the UK, or moving to the UK during the transition period, you will, if you intend to stay after 2020, have to apply for settled status:
EU Settlement Scheme - you will find all information via this link
For information about Swedish citizenship, see the Swedish Migration Agency’s website.
Moving to or living in Sweden, see The British Government: Living in Sweden
You will also find useful information on The Swedish Tax Agency’s (Skatteverket) website.
During the transition period there will be no changes in practice for citizens. As a British citizen you will be able to travel to Sweden as before brexit and the same applies for Swedish citizens travelling to the UK.
Regarding the right of UK nationals to continue living and working in Sweden under the Withdrawal Agreement, please see further information from the Swedish Government here.