The Swedish O can take on four sounds. Two short and two long ones. Unfortunately for you, there are no real rules which tell you which sound to use. That is something you have to learn as you go.
Langes O
- half closed
- uses the phonetic sign [oː]
lova
promise
son
son
- closed
- uses the phonetic sign [uː]
bok
book
mos
puree, mush, squish
Kurzes O
- half open
- uses the phonetic signn [ɔ]
- like O in Jonny
hoppa
jump
kopp
cup, mug
- closed
- uses the phonetic sign [ʊ]
blomma
flower, blossom
bonde
farmer