EDIT: Many thanks to Nelson for helping me revise. Any remaining mistakes are my responsibility.
I was a hero, then I took an arrow to the knee.
Ic/æðeling: “Adventurer” is a French word, so I had a difficult time translating it. The closest approximations I could come up with were “hero” and “wanderer.” Since “wanderer” usually has an elegiac tone in OE, I went with “hero.” “Ic” and “æðeling” are both in nominative singular case.
wæs: “Wæs” is first person simple past tense, the only grammatical tense OE uses in the past tense. The simple past can encompass a number of meanings. While it is possible to use the verb “to use” as an auxiliary for the infinitive “to be,” such constructions in OE are technically adjectival, and the verb “to use” is only used in the sense that one would use a sword, so it would not be a good equivalent.
nom: On recommendation, I’ve used the first person of “nimian.”
flān: “Arrow.”
þām cnēowe: The preposition “tō” is best used with the dative case to indicate “to” or “toward,” though considering dialectical differences, genitive case would be just as accurate. “Cnēo” declines as a strong noun; the definite article is declined accordingly.
I was a king, then I took an arrow to the eye.
The picture here is Harold Godwinson from the Bayeux Tapestry, the last Anglo-Saxon king who was slain by an arrow in the eye. The same rules apply here as above, save that “ēage” is a weak neuter noun of the –e ending class, which is declined the same as a strong neuter noun, save that the nominative and accusative cases are identical.


Nice!
On translation, the 1st person indicative past of fón is féng, without a suffix. You might be just as well off with nom (from niman), though I’m not sure that there’s a perfect verb available. For ‘arrow’, flán or strǽl would probably be better – anga basically means ‘sting’, which is used of an arrow metaphorically in the ‘agob’ riddle.
On ‘knee’, the dative should be cneowe. It’s a strong noun (a wa-stem); if it were weak, the dative would be **cneowan.
The temporal/resultative sense of þá seems a little weak here, and I want to read this as ‘I was a hero when I took an arrow to the knee’. It doesn’t quite capture the modern English either, but you might try using oð instead? Just a thought.
Yay! Finally, someone who can give me translation advice! I spent hours on these words and was never certain about any of them (and also couldn’t get ahold of original text with the most problematic ones).
So “niman” can be translated with the idiomatic “take” as well as the literal “seize,” just like in MnE?
Of course! “Oð” makes so much more sense. I was so fixated on trying to figure out that subordinating conjunction that I didn’t consider other ways to phrase it in MnE. Again, thank you!
niman has a pretty wide range of uses that resemble those of ‘take’ pretty closely, from literal senses of seizing (of swords and the like) to some more extended cases (waves taking a dragon’s corpse) to the entirely metaphorical (pleasure, peace, teaching, anger, etc.). The Bosworth-Toller entry surveys the range of uses pretty well: http://web.ff.cuni.cz/cgi-bin/uaa_slovnik/gmc_search_v3?cmd=viewthis&id=bt:b0721:20
I was just thinking the other day: “I used to be a 4.0 GPA student, then I took an Astronomy class to the knee”. Funny you should post these today.