Var försiktig med foten i dag, annars måste du vila längre.

Yes, var can mean where, but here Var is the imperative form of vara (to be), so it means be.

So:

• Var försiktig = Be careful

This imperative is irregular, which is why it is not something like vara or bär. You just have to learn var! as the command form of vara.

Context makes the meaning clear:

• Var är du? = Where are you?
• Var försiktig! = Be careful!

Because försiktig describes the implied subject du (you), not the way an action is done.

In this sentence, the full idea is basically:

• Du ska vara försiktig = You should be careful

With a singular person, Swedish normally uses the basic form of the adjective in this kind of predicate:

• du är försiktig
• var försiktig

Försiktigt would usually be used:

• with a neuter noun
• or as an adverb-like form in some contexts

For example:

• Det är försiktigt = That is careful/cautious
• Kör försiktigt = Drive carefully

But when speaking to one person, Var försiktig is the natural form.

It can mean both, depending on context.

In this sentence, försiktig means something like:

• careful
• cautious
• gentle

Because the sentence is about a foot, it suggests:

• don’t put too much strain on it
• don’t move carelessly
• take care not to make it worse

So Var försiktig med foten is very natural advice if someone has an injury.

Here med is part of the expression vara försiktig med, which means:

• to be careful with
• to be careful about

So:

• Var försiktig med foten = Be careful with your foot

The preposition is just what Swedish uses in this expression. English and Swedish often match here quite well:

• be careful with X
• vara försiktig med X

Swedish often uses the definite form for body parts when it is already obvious whose body part is meant.

So instead of saying:

• din fot = your foot

Swedish often prefers:

• foten = literally the foot

This is especially common when the owner is clear from the context.

So:

• Var försiktig med foten sounds natural
• Var försiktig med din fot is possible, but it sounds more explicit and often less natural in an everyday sentence like this

This is a very common pattern with body parts in Swedish.

Yes, both i dag and idag are used.

They both mean:

• today

Traditionally, i dag was written as two words, and many people still prefer that spelling in more careful writing. Idag is also very common and accepted.

So these are both fine:

• i dag
• idag

The meaning does not change.

Annars means:

• otherwise
• or else
• if not

It introduces the consequence of not following the advice.

So the sentence structure is:

• Be careful with your foot today
• otherwise, you’ll have to rest longer

It is a very common Swedish word for warnings and consequences.

Examples:

• Skynda dig, annars missar du tåget. = Hurry up, otherwise you’ll miss the train.
• Ta jackan, annars fryser du. = Take your jacket, otherwise you’ll be cold.

Because Swedish main clauses follow the V2 rule: the finite verb usually comes in the second position.

In a basic main clause, you can have:

• Du måste vila längre.

But when annars is moved to the front, the verb must come right after it:

• Annars måste du vila längre.

So the order becomes:

1. annars
2. måste
3. du
4. vila längre

This kind of inversion is one of the most important word-order rules in Swedish.

Compare:

• Du måste vila längre.
• I morgon måste du vila längre.
• Annars måste du vila längre.

Because Swedish often uses the present tense to talk about the future when the context already makes the time clear.

So:

• annars måste du vila längre

literally looks like present tense, but in context it means:

• otherwise you will have to rest longer

This is very normal in Swedish.

If Swedish wants to be more explicit, it could say something like:

• annars kommer du att behöva vila längre

But that is longer and heavier. In ordinary speech, måste du vila längre is completely natural.

Not exactly. Längre means longer, not simply more.

Here it refers to duration:

• vila längre = rest longer / rest for a longer time

That is different from vila mer, which would mean:

• rest more

Mer focuses on quantity or degree. Längre focuses on time.

So in this sentence, längre is the right choice because the idea is that recovery time will increase.

It is addressing one person, because of du.

Also, Var försiktig is the natural imperative when speaking to one person.

If you were speaking to several people, you would normally change the pronoun and adjective:

• Var försiktiga ... annars måste ni vila längre.

So:

• du = one person
• ni = more than one person, or sometimes polite singular in some contexts

In the given sentence, it is clearly singular.